The Interplanetary Internet, Vint Cerf Speaking

Vint Cerf, one of the fathers of the Internet, is working on expanding the 'net into outer space. Cerf has worked with NASA and JPL to develop a new set of protocols that can stand up to the unique environment of space, where orbital mechanics and the speed of light make traditional networking extremely difficult.

"So we began looking at the possibilities of TCIP/IP as a protocol for interplanetary communication. We figure it worked on Earth and it ought to work on Mars. The real question was, “Would it work between the planets?” And the answer turned out to be, “No.”

"The reason for this is two-fold: First of all, the speed of light is slow relative to distances in the solar system. A one-way radio signal from Earth to Mars takes between three and half and 20 minutes. So round trip time is of course double that. And then there’s the other problem: planetary rotation. If you’re communicating with something on the surface of the planet, it goes out of communication as the planet rotates. It breaks the available communications and you have to wait until the planet rotates back around again. So what we have is variable delay and disruption, and TCP does not do terribly well in those kinds of situations.

"One of the things that the TCP/IP protocols assume is that there isn’t enough memory in each of the routers to hold anything. So if a packet shows up and it’s destined for a place for which you have an available path, but there isn’t enough room, then typically the packet is discarded.

"We developed a new suite of protocols that we called the Bundle protocols, which are kind of like internet packets in the sense that they’re chunks of information. They can be quite big and they basically get sent like bundles of information. We do what’s called storing forward, which is the way all packet switching works. It’s just in this case the interplanetary protocol has the capacity to store quite a bit, and usually for quite a long time before we can get rid of it based on connectivity to the next hop.

This software is already in use in the two orbiters around Mars, as well as the Spirit and Opportunity rovers.

The Venus Equilateral Relay Station was a modern miracle of engineering if you liked to believe the books. Actually, Venus Equilateral was an asteroid that had been shoved into its orbit about the Sun, forming a practical demonstration of the equilateral triangle solution of the Three Moving Bodies. It was a long cylinder, about three miles in length by about a mile in diameter...

This was the center of Interplanetary Communications. This was the main office. It was the heart of the Solar System's communication line, and as such, it was well manned. Orders for everything emanated from Venus Equilateral.

Be sure to read the rest of this fascinating interview with Vint Cerf at Wired.

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